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        <h1 class="title">NodeJS中的Buffer</h1>
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                <time datetime="2018-11-05T06:04:55.000Z" itemprop="datePublished" class="page-time">
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            <ol class="post-toc"><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#Buffer介绍"><span class="post-toc-number">1.</span> <span class="post-toc-text">Buffer介绍</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#新建Buffer"><span class="post-toc-number">2.</span> <span class="post-toc-text">新建Buffer</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#Buffer使用"><span class="post-toc-number">3.</span> <span class="post-toc-text">Buffer使用</span></a></li></ol>
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        <h1 class="post-card-title">NodeJS中的Buffer</h1>
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            <time class="post-time" title="2018-11-05 14:04:55" datetime="2018-11-05T06:04:55.000Z"  itemprop="datePublished">
2018-11-05
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            <h3 id="Buffer介绍"><a href="#Buffer介绍" class="headerlink" title="Buffer介绍"></a>Buffer介绍</h3><p><strong>为什么要用Buffer？</strong></p>
<ol>
<li>在Node/ES6 出现之前，前端工程师只需要进行一些简单的额字符串或者ODM操作就可以满足业务需求了，所有对二进制数据比较陌生。</li>
<li>在node出现之后，前端工程师面对的技术场景发送了变化，可以深入到网络传输、文件操作、图片处理等领域。而这些操作与二进制数据紧密相关。</li>
<li>在Node中的Buffer，是一个二进制数据容器，数据结构和数组类似，专门用于Node中的数据放。</li>
</ol>
<h3 id="新建Buffer"><a href="#新建Buffer" class="headerlink" title="新建Buffer"></a>新建Buffer</h3><p><code>Buffer.alloc(size[, fil[,encoding]])</code><br><code>size</code>:新建的buffer期望的长度<br><code>fill</code>用来预填充新建的Buffer的值 默认0<br><code>encoding</code>: 编码格式  默认：utf-8<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">/*</span><br><span class="line">        十六进制：00- ff</span><br><span class="line">        十进制 ：0- 255</span><br><span class="line">        二进制： 00000000- 11111111</span><br><span class="line">        0 / 1 代表一位 == 比特 </span><br><span class="line">        8bit = 1B</span><br><span class="line">        1kb = 1024 B</span><br><span class="line">        1mkb= 1024Kb</span><br><span class="line">        1GB = 1024m</span><br><span class="line">        1TB = 1024GB</span><br><span class="line"></span><br><span class="line">*/</span><br><span class="line"></span><br><span class="line">// 2. Buffer.alloc(size[, fill[, encoding]])</span><br><span class="line">/*</span><br><span class="line">类数组使用即可 可遍历 可选择下标等等</span><br><span class="line">初始化： 确定的长度 不能改变</span><br><span class="line">填充值</span><br><span class="line"></span><br><span class="line">*/</span><br><span class="line">let buffer2= Buffer.alloc(10);//创建了一个长度是10的buffer</span><br><span class="line">buffer2[0]= 10;//可以像使用数组一样使用buffer </span><br><span class="line">buffer2[1]= oxfc;//传一个十六进制的直接取后两位 fc</span><br><span class="line">buffer2[30]= 1;//这点和数组不同 溢出隐藏 </span><br><span class="line">console.log(buffer2);</span><br></pre></td></tr></table></figure></p>
<h3 id="Buffer使用"><a href="#Buffer使用" class="headerlink" title="Buffer使用"></a>Buffer使用</h3><p><strong>使用新方法使用Buffer </strong></p>
<ol>
<li>Buffer.form(str):将一个字符串转换成buffer</li>
<li>Buffer.alloc(size):创建一个指定大小的buffer</li>
<li>Buffer.alloUnsafe(size):创建一个指定大小的buffer，但是可能包含敏感数据。<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">// 历史方法</span><br><span class="line">// let buffer = new Buffer(10);//类似 Array(10) 创建十个空间</span><br><span class="line">// console.log(buffer)// &lt;Buffer 00 00 00 00 00 00 00 00 00 00&gt;</span><br><span class="line"></span><br><span class="line">//1. 字符串转成二进制</span><br><span class="line">let str= &apos;www.zhangningle.top&apos;;</span><br><span class="line">let buffer= Buffer.from(str);</span><br><span class="line">console.log(buffer);//&lt;Buffer 77 77 77 2e 7a 68 61 6e 67 6e 69 6e 67 6c 65 2e 74 6f 70&gt;</span><br><span class="line">//把buffer转成十进制的</span><br><span class="line">console.log(buffer.toString())//www.zhangningle.top</span><br><span class="line">// 汉字转换成二进制后 一个汉字要用三个字节表示</span><br></pre></td></tr></table></figure>
</li>
</ol>
<p><strong>Buffer总结点：</strong></p>
<ol>
<li>Buffer的结构和数组很像，操作方法也和数组很类似。</li>
<li>Buffer中是以二进制的方式储存数据的</li>
<li>Buffer是Node自带的，不需要引入，直接可以使用。</li>
</ol>

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